1. Field of the invention
This invention relates to a disc controlling device for controlling a disc-shaped recording medium run in rotation at a constant angular velocity, such as a hard disc.
2. Description of Related Art
Heretofore, in a device adapted for controlling a disc-shaped recording medium, such as a hard disc, has an internal data transfer rate for the inner disc rim side different from that for the outer disc rim side. That is, since a hard disc is basically controlled for rotation to a constant angular velocity (CAV), the data transfer rate becomes higher on the outer disc rim side than that on the inner disc rim side. As an example, there is such a hard disc device in which the data transfer rate for the inner disc rim side and that for the outer disc rim side are 47.5 Mbps and 72 Mbps, respectively.
Thus, in designing a system employing a hard disc device, there is no alternative but to use the slower data transfer rate, that is the rate for the inner disc rim side, as a reference, or to use only a disc portion providing a faster data transfer rate, that is the outer disc rim side.
However, if the slower rate is used as a reference, system performance occasionally cannot be improved, whereas, if only the disc portion providing a faster rate is used, the hard disc cannot be exploited effectively.